Marker board



FIG. 1 is a front isometric view of the marker board showing the new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a right side elevation view thereof;

FIG. 5 is a top plan view thereof; and,

FIG. 6 is a bottle plan view thereof. 

The ornamental design for a marker board, as shown and described. 